Production of dense coke by retarding froth formation during coking



May 8, 1956 c. B. WENDELL, JR 2,744,856

PRODUCTION OF DENSE COKE BY RETARDING TH FORMATION DURING COKING FRO Filed ril 21, 1954 1 20 I7 j g 54M, 2?. 7W 472 Q47? PRODUCTION OF DENS E' COKE BY RETARDING FROTH FORMATION DURING COKING' Charles B. Wendell, Jr., Canton, Mass.

Application April 21, 1954, Serial No. 424,583 7 Claims. (Cl. 20232) This invention relates to the production of coke and comprises a new and improved process for producing dense coke from coal, pitch, petroleum residues and the like.

As is well known .in the. art, coke is produced byheating a carbonaceous material in the absence of oxygen. The volatile fractions of the material are vaporized and driven off leaving behind solid carbon as residue. During the heating the cokingbody boils as. the, volatiles separatev out and subsequently solidifies as a porous mass of carbon. Certain types of carbonaceous materials swell substantially and solidify in'their swollen condition. In any case,coke as produced is highly porous and the highest density cokes are not very dense by other standards.

As between cokes used. in: various industries density is very important. For many industrial uses low density cokes are unsuitable or' at best are, inferior tothose of higher density. For instance, low density cokes cannot be used satisfactorily in electrodes nor for carburizing steel. Furthermore, they are bulky and expensive to handle and ship.

In order to obtain dense cokes by known techniques, it has'heretofore been necessary to charge the coker with a raw material or blends of raw materials which naturally yields dense coke. Thus, many otherwise suitable, coking stocks cannot be used because the resulting coke-.has insuflicient density. To the best of myknowledge-there is no process or apparatus by or in which, heretofore, high density coke could be produced from carbonaceous materials ordinarily yielding low density coke.

I have discovered that high density coke can be produced from any carbonaceous coking material which will become liquid and froth when heated to coking temperature by distributing over the surface of the coking body hydrocarbon liquids which are essentially noncoking and will themselves vaporize and flow from the cokihgchamher with the volatile compounds driven from the coking charge. Preferably, I reflux to the coking body the condensed volatiles thus driven therefrom.

It is the principal object of my invention to provide ice coking bed a, portion of the non-coking volatile liquids driven therefrom as suchprocedure is particularlyconvenient. For reasons that will be apparent the process of my invention is most advantageously, carried out in thewell-kno'wn flat oven heated through the floor. i

Quite unexpectedly the distribution of volatilehydrocarbons on the coke bed in the manner described hasbeen found substantially to increase the density of the product. It had been supposed that the introduction of a volatile hydrocarbon in this'manner would have no eifect because at the temperature prevailing in the coke oven that material must of necessity'return to the vapor state. How ever, I have discovered that even volatile non-coking hydrocarbons remain liquid for a sufficient time to serve as a blanket and to cause densification of theicoke. bed.

The features of my invention will best be understood and appreciated from the following description of apparatus which may be employed in carrying out my novel process, shown in the accompanying drawings in which:

Fig. 1 is a view of a coking oven and auxiliary equipment partly in elevation and partly in vertical section, and

Fig. 2 is a sectional view on theline 2-2 of Fig. 1.

The apparatus comprises broad oven 10 provided with heating fiues 12 beneath a floor 14 constructedof refractory brick. A charging port 16, having a cover 17, and overhead product take ofi conduit 18 are located at convenient points in the. dome of oven 10. The oven as thus far described is generally typical of broad ovens such as that described in United States Letters Patent No.

2,234,171, Hughes.

tures and then delivering a volatile liquid hydrocarbon Conduit 18 branches into stack 20 and conduit 22, the latter conduit leading into acondenser 24 of any suitable design. A valve 26'is provided in stack 20 and is closed when'overhead products are being sent to condenser 24.

There is alsoprovided in the dome of oven 10 a plurality of sprayxheads 30 distributed over the dome area in such a way that the. liquids introduced therethrough will bemore or' less uniformly deposited over the entire surface of' the coking" body. Alternatively, the spray heads may be positioned at convenient points in the side wallsof oven 10; or any other suitable means may be employed whereby to depositthe liquids-uniformly over the coking body. As hereshownspray heads 30 are centered in and disposed along thelongitudinal axis of the oven 10.-

Liquids are supplied to spray heads 30 by conduit'32 .leading from condenser 24 through a pump-34. If liquids other than those obtained from condenser 24 are to be used they may be. introducediinto conduit 32 ahead of the pump through a pipe 36. Products from the condenser not recycled to the oven 24 may be recovered through pipe 38 leading from a point near'the bottom of the condenser.

In operation, heat is applied to the oven through the floor from fiues 12 until. the oven has reached coking temperature (i. e. about 1500 F.). Then, a charge of raw coking material, comprising coal, pitch, petroleum residue or thelike, is introduced through. feedport. 16 while the heat is continuously applied. As thefeed is heated within the oven its non-coking volatile components commence to volatilize, audit is soon converted to a frothing mass. I

The volatile products pass overhead into the conduit 18. In the initial stage of operation, these volatile products are contaminated with occluded carbon particles, which form due to the complete pyrolysis of some of the gaseous constituents produced. Accordingly, valve 26 is initially adjusted to its open position to permit escape of the contaminated overhead products from oven 10. But as soon as the overhead products are cleared of the occluded carbon particles, the valve 26 is closed and Ii the overhead products are then conveyed through conduit 22 to condenser 24.

Within the condenser, which may be of the bubble-cap or other suitable type, the greater portion of the overhead products are converted from the gaseous to the liquid state and are removed therefrom as such. Uncondensed vapors may be vented through pipe 40 to the atmosphere or to recovery for use as gaseous fuel.

The condensed products or other liquids are propelled through conduit 32 by the pump 34 and are delivered into the oven through spray nozzles 30. These liquids are sprayed evenly over the surface of the coking mass, thereby reducing the frothing of the mass and increasing the density of the coke. The amount of liquid to be sprayed into oven 10 will vary, depending upon the nature of the raw material and the desired coke density.

In the following'example are set forth the results of several runs made in accordance with the invention herein described in which the coking charge was bituminous coal normally yielding low density coke and the liquids sprayed on the charge surface were condensed volatiles from the charge.

The foregoing runs indicate that on the average the density of the product was increased 20.7% by treatment of the raw material in accordance with the process above described. The importance of this improvement is of very great significance to the industry.

While I am unable to explain the exact reasons for the imrovements realized from the practice of the process of my invention, it seems probable that the effect of the deposition of liquids upon the frothing coking charge is to reduce the rate at which the raw material volatilizes. Accordingly, it would follow that the frothing tendencies of the coking mass are diminished by the liquid blanket. This results in the formation of coke which has fewer and smaller gas holes than cokes produced in accordance with usual procedures.

This application is filed as a substitute and continuation in part of my co-pending application Ser. No. 259,056, filed November 30, 1951, and now abandoned.

Having thus disclosed my invention and described in detail an illustrative manner of practicing it, I claim as new and desire to secure by Letters Patent:

1. In the production of coke, a process for increasing the density of the coke which comprises continuously distributing a volatile liquid hydrocarbon over the surface of the charge while frothing during coking thereby inhibiting frothing of the charge and vaporizing substan tially all of said hydrocarbon, and removing said vapors from the presence of the charge.

2. The process of claim 1 in which the liquid hydrocarbon is continuously delivered to the surface of the frothing coking charge until substantially all of the volatile components thereof have been removed.

3. The process of claim 1 in which the liquid hydrocarbon deposited upon the frothing coking charge is recycle material composed of condensed volatiles from the said charge.

4. A process for producing dense coke from coal characterized by heating from the bottom a charge of coal distributed in a horizontally disposed bed of substantially uniform thickness to approximately 1500 E, and thus converting it to a frothing condition and spraying a substantially completely vaporizable hydrocarbon oil over the surface of the heated bed thereby retarding the rate of vaporization of the volatile constituents of the coal while the latter is being converted to coke and vaporizing the oil, and recovering the vapors produced by the heating.

5. In a process for producing coke by heating from below a relatively shallow, horizontally disposed bed of carbonaceous material that tends to be converted to frothing condition on heating, the improvement which consists in uniformly distributing over the surface of the bed, while the bed is frothing at coking temperature a volatile liquid hydrocarbon which is sutiiciently noncoking that it substantially completely vaporizes and does not appreciably contribute to coke formation and continuing the distribution of said liquid hydrocarbon until all volatile components of the bed have been removed, whereby the resulting coke is densified to a greater extent than if no liquid had been distributed thereon.

6. The process of claim 5 in which the distributed liquid hydrocarbon is recycle material composed of condensed volatiles from the charge.

7. In the production of coke from a bed of carbonaceous coking material which when heated to coking temperature normally tends to become liquid and froth, a process for increasing the density of the coke produced which comprises the steps of distributing over the top surface of the bed of carbonaceous coking material, while the bed is in the frothing stage and being subjected to coking temperatures by heating from the bottom, in amount sufficient to retard said frothing and significantly increase the density of the resulting coke, a liquid hydrocarbon Which is so volatile relative to its coking tendency that it is essentially noncoking and is mostly vaporized and removed from the coking chamber with other volatile by-products.

References Cited in the file of this patent UNITED STATES PATENTS 105,351 McCraken July 12, 1870 705,926 Hemingway July 29, 1902 1,717,884 Knowles June 18, 1929 1,825,375 Thiele Sept. 29, 1931 1,908,133 Eglofi May 9, 1933 1,942,372 Miller Jan. 2, 1934 1,942,980 Rhodes Jan. 9, 1934 1,944,872 Andrews et al Ian. 30, 1934 2,114,416 Donnelly Apr. 19, 1938 2,347,076 Boynton et a1 Apr. 18, 1944 2,406,810 Day Sept. 3, 1946 2,656,309 Brown Oct. 20, 1953 OTHER REFERENCES Coal, Coke and Coal Chemicals, by Wilson and Wells (McGraw-Hill), 1950. 

7. IN THE PRODUCTION OF COKE FROM A BED OF CARBONACEOUS COKING MATERIAL WHICH WHEN HEATED TO COKING TEMPERATURE NORMALLY TENDS TO BECOME LIQUID AND FROTH, A PROCESS FOR INCREASING THE DENSITY OF THE COKE PRODUCED WHICH COMPRISES THE STEPS OF DISTRIBUTING OVER THE TOP SURFACE OF THE BED OF CARBONACEOUS COKING MATERIAL, WHILE THE BED IS IN THE FROTHING STAGE AND BEING SUBJECTED TO COKING TEMPERATURES BY HEATING FROM THE BOTTOM, IN AMOUNT SUFFICIENT TO RETARD SAID FROTHING AND SIGNIFICANTLY INCREASE THE DENSITY OF THE RESULTING COKE, A LIQUID HYDROCARBON WHICH IS SO VOLATILE TO ITS COKING TENDENCY THAT IT IS ESSENTIALLY NONCOKING AND IS MOSTLY VAPORIZED AND REMOVED FROM THE COKING CHAMBER WITH OTHER VOLATILE BY-PRODUCTS. 